Magma Proves Undersea Volcanoes Do Explode

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Deep-sea volcanoes can explode instead of just oozing, scientists
now confirm.

The new proof — higher-than-expected levels of carbon dioxide in
the magma from a volcano off the coast of Oregon —suggests the
volcanoes may play a greater role in global climate than thought.

Of all the volcanic activity on Earth, 75 to 80 percent of it
takes place at deep-sea ridges in the middle of the oceans. Most
of these volcanoes apparently spew out huge volumes of lava
instead of
erupting explosively, as many volcanoes on land do.

It is a high level of gas trapped in a volcano's magma that
normally fuels explosive volcanic bursts. This level has long
been thought to be low at mid-ocean ridges; moreover, potential
undersea explosions would be suppressed by the crushing pressure
from the surrounding water.

However, based on volcanic ash found at certain sites, geologists
have speculated over the last decade that explosive eruptions do
take place in
deep-sea volcanoes. Now researchers say they have proof.

A team of scientists used ion beams to analyze the composition of
materials recovered from ash deposits on Axial Volcano, on the
Juan de Fuca Ridge off the coast of Oregon. Trapped within
crystals from the deposits were droplets of magma containing very
high levels of carbon dioxide. These droplets revealed that the
magma was indeed rich in gas, at concentrations high enough to
generate bubbles in the molten rock for explosive underwater
eruptions.

"Direct evidence for high carbon dioxide concentrations in a
mid-ocean-ridge volcano was unexpected and surprising,"
researcher Christoph Helo, a volcanologist at McGill University
in Montreal, told OurAmazingPlanet.

These findings suggest the amount of the
global-warming gas carbon dioxide that is released from the
deeper mantle into the Earth's atmosphere at mid-ocean ridges
falls within the higher end of past estimates, nearly 10 times
more than the lowest end. That could have key implications for
climate change.